I believe one of the main causes for pimples is hormones. Diet, exercise and good hygiene can help prevent uncontrollable zits from appealing. Especially changing your diet, It's not just junk food, greasy food, and sodas that you have to stay away from. What you need to do is cut off any food that increases your hormonal level, causing you to have a hormonal imbalance (teens are prone to that because of puberty). this includes all dairy product, tofu, etc. So say away from milk, cheese, and other dairy products and stick to eating organic meat (fish preferred). This should help clear those acne up or at least diminish the harsh ones. It's always good idea to check up on your dermatologist to see how your skin works. They can provide a medicine that's right for your skin.
I hope I helped in anyway. and good luck!